1. Field of the Invention
The present invention is related to an imaging device. More particularly, the present invention is related to an imaging device that enables obtainment of color images in a focused state regardless of the distance to a subject.
2. Description of the Related Art
An imaging device has been proposed, in which the spatial frequency properties of a lens optical system are stabilized by inserting a phase plate, and image reconstruction processes, that is, processes in which image signals are passed through reconstructing filters having properties inverse the blur properties of the imaging lens optical systems, are administered to enable obtainment of images in a focused state regardless of the distances to subjects. U.S. Patent Application Publication No. 20090147111 and Japanese Unexamined Patent Publication No. 2009-089082 describe examples of such an imaging device.
It is often the case that the aforementioned type of imaging device employs an imaging element constituted by a CCD or the like, similar to general imaging devices. In this case, a single chip color imaging element, in which a color filter constituted by R (red), G (green), and B (blue) filters for each pixel arranged in a two dimensional matrix is provided on a photoelectric converting section, is often employed, to perform imaging of color images.
U.S. Patent Application Publication No. 20090147111 and Japanese Unexamined Patent Publication No. 2009-089082 propose methods for administering the aforementioned image reconstruction process when using such a single chip color image element in detail.
First, U.S. Patent Application Publication No. 20090147111 proposes to perform the image reconstruction process separately for each of R, G, and B channels. Note that in this proposed method, a Bayer pattern color filter is employed, and therefore, with respect to the G channel, the image reconstruction process is performed on a combined G channel, which is a Gr and Gb channel on which sensitivity correction has been administered and combined. In this reconstruction process, a reconstruction filter is employed that performs convolution such that ¾ of the elements of the R and B channels become zero and 2/4 of the elements of the G channel become zero in a zigzag arrangement.
Meanwhile, Japanese Unexamined Patent Publication No. 2009-089082 proposes to generate a reconstruction filter for data of each of R, Gr, Gb, and B channels, and employing the generated reconstruction filters to independently perform reconstruction processes for each channel, in the case that such a color imaging element is employed.
In the method described in U.S. Patent Application Publication No. 20090147111, calculating processes (branched calculations) are performed for elements of which the value of the reconstruction filter is zero, and therefore it is recognized that there is a problem of high calculation costs. In addition, with respect to memory capacity for storing data of the reconstruction filter, four times the memory capacity is necessary for elements having values other than zero for the R and B channels, and twice the memory capacity is necessary for elements having values other than zero for the G channel. For these reasons, this method is not economical.
Meanwhile, in the method described in Japanese Unexamined Patent Publication No. 2009-089082, convolution calculating processes, which have extremely high calculation costs, are administered for all pixels. Therefore, a problem is recognized that the calculation cost is high in this case as well. In addition, it is known that the G channel greatly influences the perceived resolution of ultimately obtained images. However, because the method described in this patent document performs image reconstruction processes on the Gr channel and Gb channel separately, there is a problem that high frequency components are likely to be lost in reconstructed images.